/*
    * ====================================================================
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.hc.core5.http2.impl.nio;
  
  import java.io.IOException;
  import java.net.SocketAddress;
  import java.nio.ByteBuffer;
  import java.nio.channels.ByteChannel;
  
  import javax.net.ssl.SSLSession;
  
  import org.apache.hc.core5.annotation.Internal;
  import org.apache.hc.core5.http.EndpointDetails;
  import org.apache.hc.core5.http.HttpException;
  import org.apache.hc.core5.http.ProtocolVersion;
  import org.apache.hc.core5.http.impl.nio.HttpConnectionEventHandler;
  import org.apache.hc.core5.http.nio.command.CommandSupport;
  import org.apache.hc.core5.http2.ssl.ApplicationProtocol;
  import org.apache.hc.core5.io.CloseMode;
  import org.apache.hc.core5.io.SocketTimeoutExceptionFactory;
  import org.apache.hc.core5.reactor.IOEventHandler;
  import org.apache.hc.core5.reactor.IOSession;
  import org.apache.hc.core5.reactor.ProtocolIOSession;
  import org.apache.hc.core5.reactor.ssl.TlsDetails;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.TextUtils;
  import org.apache.hc.core5.util.Timeout;
  
  /**
   * I/O event handler for events fired by {@link ProtocolIOSession} that implements
   * client side of the HTTP/2 protocol negotiation handshake always forcing the choice
   * of HTTP/2.
   *
   * @since 5.0
   */
  @Internal
  public class H2OnlyClientProtocolNegotiator implements HttpConnectionEventHandler {
  
      private final ProtocolIOSession ioSession;
      private final ClientH2StreamMultiplexerFactory http2StreamHandlerFactory;
      private final boolean strictALPNHandshake;
  
      private final ByteBuffer preface;
  
      public H2OnlyClientProtocolNegotiator(
              final ProtocolIOSession ioSession,
              final ClientH2StreamMultiplexerFactory http2StreamHandlerFactory,
              final boolean strictALPNHandshake) {
          this.ioSession = Args.notNull(ioSession, "I/O session");
          this.http2StreamHandlerFactory = Args.notNull(http2StreamHandlerFactory, "HTTP/2 stream handler factory");
          this.strictALPNHandshake = strictALPNHandshake;
          this.preface = ByteBuffer.wrap(ClientHttpProtocolNegotiator.PREFACE);
      }
  
      @Override
      public void connected(final IOSession session) {
          try {
              final TlsDetails tlsDetails = ioSession.getTlsDetails();
              if (tlsDetails != null) {
                  final String applicationProtocol = tlsDetails.getApplicationProtocol();
                  if (TextUtils.isEmpty(applicationProtocol)) {
                      if (strictALPNHandshake) {
                          throw new HttpException("ALPN: missing application protocol");
                      }
                  } else {
                      if (!ApplicationProtocol.HTTP_2.id.equals(applicationProtocol)) {
                          throw new HttpException("ALPN: unexpected application protocol '" + applicationProtocol + "'");
                      }
                  }
              }
              writePreface(session);
          } catch (final Exception ex) {
              session.close(CloseMode.IMMEDIATE);
              exception(session, ex);
         }
     }
 
     private void writePreface(final IOSession session) throws IOException  {
         if (preface.hasRemaining()) {
             final ByteChannel channel = session;
             channel.write(preface);
         }
         if (!preface.hasRemaining()) {
             final ClientH2StreamMultiplexer streamMultiplexer = http2StreamHandlerFactory.create(ioSession);
             final IOEventHandler newHandler = new ClientH2IOEventHandler(streamMultiplexer);
             newHandler.connected(session);
             ioSession.upgrade(newHandler);
         }
     }
 
     @Override
     public void inputReady(final IOSession session, final ByteBuffer src) {
         outputReady(session);
     }
 
     @Override
     public void outputReady(final IOSession session) {
         try {
             if (preface != null) {
                 writePreface(session);
             } else {
                 session.close(CloseMode.GRACEFUL);
             }
         } catch (final IOException ex) {
             session.close(CloseMode.IMMEDIATE);
             exception(session, ex);
         }
     }
 
     @Override
     public void timeout(final IOSession session, final Timeout timeout) {
         exception(session, SocketTimeoutExceptionFactory.create(timeout));
     }
 
     @Override
     public void exception(final IOSession session, final Exception cause) {
         try {
             CommandSupport.failCommands(session, cause);
         } finally {
             session.close(CloseMode.IMMEDIATE);
         }
     }
 
     @Override
     public void disconnected(final IOSession session) {
         CommandSupport.cancelCommands(session);
     }
 
     @Override
     public SSLSession getSSLSession() {
         final TlsDetails tlsDetails = ioSession.getTlsDetails();
         return tlsDetails != null ? tlsDetails.getSSLSession() : null;
     }
 
     @Override
     public EndpointDetails getEndpointDetails() {
         return null;
     }
 
     @Override
     public void setSocketTimeout(final Timeout timeout) {
         ioSession.setSocketTimeout(timeout);
     }
 
     @Override
     public Timeout getSocketTimeout() {
         return ioSession.getSocketTimeout();
     }
 
     @Override
     public ProtocolVersion getProtocolVersion() {
         return null;
     }
 
     @Override
     public SocketAddress getRemoteAddress() {
         return ioSession.getRemoteAddress();
     }
 
     @Override
     public SocketAddress getLocalAddress() {
         return ioSession.getLocalAddress();
     }
 
     @Override
     public boolean isOpen() {
         return ioSession.isOpen();
     }
 
     @Override
     public void close() throws IOException {
         ioSession.close();
     }
 
     @Override
     public void close(final CloseMode closeMode) {
         ioSession.close(closeMode);
     }
 
 }